MONTPELIER — A key Vermont Republican activist is urging party members to skip voting for Scott Milne and the other declared candidates for the party’s gubernatorial nomination and write in a Libertarian instead.

The activist, Darcie Johnston, who managed Republican nominee Randy Brock’s campaign for governor in 2012, issued a statement saying she hopes people will write in the name of Libertarian Dan Feliciano on the Republican ballot in the Aug. 26 primary.

“I will be working to help him to get write-in votes to be the Republican nominee,” Johnston wrote. “Dan’s focus is on the issues that matter most to Republicans and many Republicans are already supporting him.”

Johnston is a leading critic of Gov. Peter Shumlin’s push for a universal, state-run health care system and the founder of a group devoted to defeating it.

She said Feliciano, 51, a business consultant from Essex Junction who has had health insurance companies among his clients, has the best background for a gubernatorial candidate. He’s vowing to stop the state’s push toward universal health care.

Feliciano did not immediately reply to a message left for him Thursday. But on his blog, he has sharply criticized both Shumlin’s health care initiative, which has backing from majority Democrats in the Legislature, and Milne’s stance on it.

“Scott Milne’s shocking weak and timid position on single payer has revealed him to be another big government Republican,” Feliciano wrote. “By not opposing single payer, Milne opens the door to bigger government, higher spending, higher taxes, and lower economic growth.”

Milne told political columnist Paul Heintz of Burlington’s Seven Days weekly newspaper last month that he was “agnostic” on Shumlin’s health care plan, a comment that has resulted in criticism from some Republicans.

On Thursday, Milne said in an interview that he had since determined that that choice of words was “clumsy.”

He said he is doubtful about Shumlin’s health care proposal, but will wait until more facts are available, including how much it would cost and how it would be paid for — two things the Shumlin administration has yet to reveal — before making a final determination.

He said he believed Johnston had decided to oppose her candidacy because he had failed her “litmus test” of providing strong enough opposition to single-payer health care.

“I’m relatively new to this, but my sense is Darcie’s doing me a favor by pointing out that I’m a practical and thoughtful potential leader of the Vermont who’s going to develop policy based on facts and not ideology,” he said.

Republican Party Chairman David Sunderland said that if Republicans familiarize themselves with some of the petitions of the Libertarian Party under whose banner Feliciano is running, they will be given pause.

Among the party’s positions with which most Republicans disagree, Sunderland said, is a call for amnesty for all convicted nonviolent drug offenders.